Adolescent sexually transmitted HIV infection is a growing and significant problem in Mexico. The broad objective of this project is to test the efficacy of a theory-based intervention, designed to reduce the adolescents' risk of sexually transmitted HIV. In the proposed randomized controlled trial, families [adolescents (n=936), 14 to 17 years of age and one of their parents] will be recruited from school and community settings and randomly assigned to (a) an HIV risk-reduction intervention or (b) a general health promotion control condition. Adolescents assigned to the HIV risk reduction intervention will receive an intervention developed for US Latino adolescents and tailored for Mexican youth; their parent will receive similar content and also content to improve parent-adolescent communication. Adolescents assigned to the control condition will receive information that focuses on other behavior-linked diseases including cancer, and diabetes; their parent will receive similar content. Interventions will be structurally similar. This research is based on an ecodevelopmental framework and considers individual, microsystem, and macrosystem influences on HIV sexual risk behavior. Adolescent data will be collected preintervention, immediately post-intervention, and at 3, 6, and 12 month follow-ups. Adolescent outcome measures include self-reported HIV risk-associated sexual behavior and hypothesized mediators of intervention effects (i.e. attitudes, beliefs, subjective norms, self-efficacy, and behavioral intentions). Parental outcome measures include comfort with, content, and frequency of parent-adolescent communication. Repeated measures analysis of variance, planned contrasts, multiple regression, and logistic regression analysis will be performed to address 4 Specific Aims: First, does the HIV risk-reduction intervention reduce self-reported HIV risk-associated sexual behavior compared with the control condition? Second, are the intervention's effects moderated by key individual (preintervention sexual experience, gender, age), microsystem (family communication) and macrosystem (Mexican cultural values)? Third, do theory-based mediators explain the intervention's effects on self-reported behavior? Fourth, does the parental component of the HIV risk-reduction intervention increase the amount and comfort with parental communication as compared with the control intervention? This study builds upon the investigative teams' prior research conducting randomized controlled interventions for US Latino and African-American adolescents and is an important contribution in curbing the increasing threat of HIV among Mexico's youth.